First, as an application example of a voltage divider circuit, a case is described with reference to FIG. 1, in which a constant voltage output circuit, which uses a voltage divider circuit including resistors, is manufactured on a semiconductor wafer.
As illustrated in FIG. 1, the constant voltage output circuit includes a reference voltage generating circuit, an amplifier, the voltage divider circuit, and an output transistor. The constant voltage output circuit supplies a constant output voltage. An example of the voltage divider circuit used herein is illustrated in FIG. 2. Trimming fuses 2 are arranged in parallel to resistors 1 connected in series. When the fuse 2 is cut, a current flows through the resistor arranged in parallel thereto, thereby changing a division ratio of the voltage divider circuit. In this manner, an adjustment can be made to obtain a desired voltage.
The constant voltage output circuit is manufactured through a semiconductor wafer process, and varies in manufacturing. Thus, if no measure is taken, a reference voltage for determining a magnitude of a low voltage output varies. Thus, after the voltage divider circuit is manufactured, the division ratio of the voltage divider circuit is precisely adjusted depending on the variation of the reference voltage to adjust the reference voltage. With this, an output voltage of the constant voltage output circuit can be set substantially constant.
In particular, in recent years, higher accuracy of ±1% or ±0.5% has been demanded for the output voltage supplied from the constant voltage output circuit. By this reason, in Patent Literature 1, as illustrated in FIG. 3, a coarse adjustment circuit is trimmed, and an output voltage is measured thereafter so that a fine adjustment circuit is trimmed in accordance with the measured value. In this way, high accuracy of an output voltage of a constant voltage output circuit is achieved. Further, in Patent Literature 2, as illustrated in FIG. 4, trimming resistors 1R, 3R, and 4R are sequentially arranged around a reference resistor Rref, thereby suppressing a manufacturing variation to be small.